U.S. patent number 6,138,003 [Application Number 08/978,910] was granted by the patent office on 2000-10-24 for system and method for authorization of location services.
This patent grant is currently assigned to Ericsson Inc.. Invention is credited to Stephen Hayes, Christopher H. Kingdon, Maya Roel-Ng, Bagher R. Zadeh.
United States Patent |
6,138,003 |
Kingdon , et al. |
October 24, 2000 |
System and method for authorization of location services
Abstract
A telecommunications system and method is disclosed which
performs authorization checks prior to allowing a location service
to position a mobile terminal within a cellular network. The
various checks involve ensuring that the requesting agency has
authorization to request positioning of mobile terminals,
determining whether positioning of mobile terminals is allowed
within the cellular network that the mobile terminal is currently
located in, verifying the authenticity of the identity of the
mobile positioning center, ascertaining whether the mobile
subscriber has allowed the requesting agency to position the mobile
terminal, and confirming that all relevant criteria for positioning
have been met by both the mobile subscriber and the requesting
agency.
Inventors: |
Kingdon; Christopher H.
(Garland, TX), Zadeh; Bagher R. (Dallas, TX), Roel-Ng;
Maya (Plano, TX), Hayes; Stephen (Carrollton, TX) |
Assignee: |
Ericsson Inc. (Research
Triangle Park, NC)
|
Family
ID: |
25526513 |
Appl.
No.: |
08/978,910 |
Filed: |
November 26, 1997 |
Current U.S.
Class: |
455/410; 455/411;
340/7.27; 340/5.74; 455/456.5; 455/456.2 |
Current CPC
Class: |
H04W
4/02 (20130101); H04W 12/02 (20130101); H04W
12/06 (20130101); H04L 63/101 (20130101); H04W
12/63 (20210101); H04W 60/04 (20130101); H04W
8/02 (20130101); H04W 12/72 (20210101) |
Current International
Class: |
H04Q
7/38 (20060101); H04B 007/12 () |
Field of
Search: |
;455/12.1,31.3,456,410,411,414,457,99,406,38.1,427,428,432,433,434,440
;340/125.44,825.49,825.54 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
|
|
|
|
|
|
|
0 600 162 A1 |
|
Aug 1993 |
|
EP |
|
92/10069 |
|
Nov 1992 |
|
WO |
|
Other References
PCT International Search Report dated Mar. 15, 1999..
|
Primary Examiner: Hunter; Daniel S.
Assistant Examiner: Tran; Pablo N.
Attorney, Agent or Firm: Jenkens & Gilchrist, P.C.
Claims
What is claimed is:
1. A telecommunications system for authorizing positioning of a
given one of a plurality of mobile stations associated with a home
network when said given mobile station is roaming in a visiting
network, said telecommunications system comprising:
a serving mobile switching center within said visiting network,
said serving mobile switching center being in wireless
communication with said given mobile station; and
a serving mobile positioning center in communication with said
serving mobile switching center, said serving mobile positioning
center being adapted to deny positioning of said given mobile
station within said visiting network in response to a determination
that positioning of any of said plurality of mobile stations is
prohibited within said visiting network.
2. The telecommunications system of claim 1, further
comprising:
a node adapted to receive a positioning request for said given
mobile station and transmit positioning request to said serving
mobile switching center.
3. The telecommunications system of claim 2, wherein said node has
an identity associated therewith, said identity and said
positioning request being sent to said mobile switching center.
4. The telecommunications system of claim 3, further
comprising:
a home mobile positioning center within said home network, said
home mobile positioning center having an identity associated
therewith; and
a home location register within said home network adapted to store
said identity of said home mobile positioning center;
wherein said serving mobile switching center is adapted to obtain
said identity of said home mobile positioning center from said home
location register, compare said identity of said home mobile
positioning center with request, and reject said positioning
request when said identity of said home mobile positioning center
does not match said identity of said node.
5. The telecommunications system of claim 4, further
comprising:
a requesting node adapted to send said positioning request to said
node;
wherein said serving mobile switching center is adapted to transmit
a denial message to said requesting node when said positioning
request is rejected.
6. The telecommunications system of claim 1, wherein said serving
mobile switching center is adapted to deny positioning of said
given mobile station within said visiting network in response to a
determination that said home network prohibits positioning of said
given mobile station within said visiting network.
7. The telecommunications system of claim 6, further
comprising:
a home location register within said home network adapted to store
data associated with said given mobile station;
wherein said serving mobile switching is adapted to obtain said
data from said home location register and use said data to make
said determination that said home network prohibits positioning of
said given mobile station within said visiting network.
8. A method for authorizing positioning of a given one of a
plurality of mobile stations associated with a home network when
said given mobile station is roaming in a visiting network, said
method comprising the steps of:
receiving a positioning request for said given mobile station at a
serving mobile switching center within said visiting network and in
wireless communication with said given mobile station;
determining whether positioning of any of said plurality of mobile
stations is allowed within said visiting network; and
if not, rejecting said positioning request.
9. The method of claim 8, wherein said step of receiving further
comprises the step of:
receiving said positioning request at a node having an identity
associated therewith; and
transmitting said positioning request and said identity to said
mobile switching center.
10. The method of claim 9, further comprising the steps of:
receiving an identity associated with a home mobile positioning
center within said home network at said mobile switching
center;
comparing said identity associated with said home mobile
positioning center with said identity of said node; and
rejecting said positioning request when said identity associated
with said home mobile positioning center does not match said
identity associated with said node.
11. The method of claim 10, wherein said step of receiving said
positioning request further comprises the step of:
transmitting said positioning request from a requesting node to
said node.
12. The method of claim 11, wherein either of said steps of
rejecting further comprises the step of:
sending a denial message from said mobile switching center to said
requesting node.
13. The method of claim 8, further comprising the steps of:
determining whether said home network prohibits positioning of said
mobile station within said visiting network; and
if so, rejecting said positioning request.
14. The method of claim 13, wherein said step of determining
whether said home network prohibits positioning of said mobile
station within said visiting network further comprises the steps
of:
receiving data associated with said mobile station at said mobile
switching center; and
using said data to determine whether said home network prohibits
positioning of said mobile station in said visiting network.
15. A telecommunications system for determining whether positioning
of a mobile station associated with a home network is allowed when
said mobile station is roaming within a visiting network, said
telecommunications system comprising:
a serving mobile switching center within said visiting network,
said serving mobile switching center being in wireless
communication with said mobile station and being adapted to deny
positioning of said mobile station in response to a determination
that said home network prohibits positioning of said mobile station
within said visiting network.
16. The telecommunications system of claim 15, further
comprising:
a home location register within said home network adapted to store
data associated with said mobile station;
wherein said serving mobile switching center is adapted to obtain
said data from said home location register and use said data to
make said determination.
17. The telecommunications system of claim 16, further
comprising:
a node having an identity associated therewith, said node being
adapted to receive a positioning request for said mobile station
and send said positioning request and said identity to said serving
mobile switching center.
18. The telecommunications system of claim 17, further
comprising:
a home mobile positioning center within said home network, said
home mobile positioning center having an identity associated
therewith;
wherein said home location register is adapted to store said
identity of said home mobile positioning center and transmit said
identity of said home mobile positioning center to said serving
mobile switching center; and
wherein said serving mobile switching center is adapted to reject
said positioning request when said identity associated with said
home mobile positioning center does not match said identity of said
node.
19. A telecommunications system for determining whether positioning
of a mobile station is allowed, said telecommunications system
comprising:
a requesting node having at least one directory number associated
therewith, said requesting node being adapted to send a positioning
request for said mobile station; and
a mobile positioning center in communication with said requesting
node to receive said positioning request, said mobile positioning
center being adapted to store said at least one directory number
for said requesting node and reject said positioning request in
response to a determination that said mobile station does not have
a call connection established towards one of said at least one
directory number of said requesting node when said positioning
request is received.
20. A method for determining whether positioning of a mobile
station within a telecommunications system is allowed, said method
comprising the steps of:
sending a positioning request for said mobile station from a
requesting node having at least one directory number associated
therewith to a mobile positioning center;
determining whether said mobile station has a call connection
established towards one of said at least one directory number;
and
if not, rejecting said positioning request.
Description
BACKGROUND OF THE PRESENT INVENTION
1. Field of the Invention
The present invention relates generally to telecommunications
systems and method for determining the location of a mobile
terminal within a cellular network, and specifically to performing
authorization checks prior to positioning the mobile terminal.
2. Background and Objects of the Present Invention
Cellular telecommunications is one of the fastest growing and most
demanding telecommunications applications ever. Today it represents
a large and continuously increasing percentage of all new telephone
subscriptions around the world. A standardization group, European
Telecommunications Standards Institute (ETSI), was established in
1982 to formulate the specifications for the Global System for
Mobile Communication (GSM) digital mobile cellular radio
system.
With reference now to FIG. 1 of the drawings, there is illustrated
a GSM Public Land Mobile Network (PLMN), such as cellular network
10, which in turn is composed of a plurality of areas 12, each with
a Mobile Switching Center (MSC) 14 and an integrated Visitor
Location Register (VLR) 16 therein. The MSC/VLR areas 12, in turn,
include a plurality of Location Areas (LA) 18, which are defined as
that part of a given MSC/VLR area 12 in which a mobile station (MS)
(terminal) 20 may move freely without having to send update
location information to the MSC/VLR area 12 that controls the LA
18. Each Location Area 12 is divided into a number of cells 22.
Mobile Station (MS) 20 is the physical equipment, e.g., a car phone
or other portable phone, used by mobile subscribers to communicate
with the cellular network 10, each other, and users outside the
subscribed network, both wireline and wireless.
The MSC 14 is in communication with at least one Base Station
Controller (BSC) 23, which, in turn, is in contact with at least
one Base Transceiver Station (BTS) 24. The BTS is the physical
equipment, illustrated for simplicity as a radio tower, that
provides radio coverage to the cell 22 for which it is responsible.
It should be understood that the BSC 23 may be connected to several
base transceiver stations 24, and may be implemented as a
stand-alone node or integrated with the MSC 14. In either event,
the BSC 23 and BTS 24 components, as a whole, are generally
referred to as a Base Station System (BSS) 25.
With further reference to FIG. 1, the PLMN Service Area or cellular
network 10 includes a Home Location Register (HLR) 26, which is a
database maintaining all subscriber information, e.g., user
profiles, current location information, International Mobile
Subscriber Identity (IMSI) numbers, and other administrative
information. The HLR 26 may be co-located with a given MSC 14,
integrated with the MSC 14, or alternatively can service multiple
MSCs 14, the latter of which is illustrated in FIG. 1.
The VLR 16 is a database containing information about all of the
Mobile Stations 20 currently located within the MSC/VLR area 12. If
a MS 20 roams into a new MSC/VLR area 12, the VLR 16 connected to
that MSC 14 will request data about that Mobile Station 20 from the
HLR database 26 (simultaneously informing the HLR 26 about the
current location of the MS 20). Accordingly, if the user of the MS
20 then wants to make a call, the local VLR 16 will have the
requisite identification information without having to
reinterrogate the HLR 26. In the aforedescribed manner, the VLR and
HLR databases 16 and 26, respectively, contain various subscriber
information associated with a given MS 20.
Determining the geographical position of a MS within a cellular
network has recently become important for a wide range of
applications. For example, positioning services may be used by
transport and taxi companies to determine the location of their
vehicles. In addition, for emergency calls, e.g., 911 calls, the
exact location of the mobile terminal may be extremely important to
the outcome of the emergency situation. Furthermore, positioning
services can be used to determine the location of a stolen car, for
the detection of home zone calls, which are charged at a lower
rate, for the detection of hot spots for micro cells, or for the
subscriber to determine, for example, the nearest gas station,
restaurant, or hospital.
Currently, as can be seen in FIG. 2 of the drawings, upon a network
positioning request, the Base Station System (BSS) (220 and 240)
serving the MS 200 generates positioning data, which is delivered
to the Mobile Switching Center (MSC) 260. This positioning data is
then forwarded to a Mobile Positioning Center (MPC) 270 for
calculation of the geographical location of the MS 200. The
location of the MS 200 can then be sent to the application 280 that
requested the positioning. Alternatively, the requesting
application 280 could be located within the MS 200 itself or within
the network (MSC/VLR 260).
In order to accurately determine the location of the MS 200,
positioning data from three or more separate Base Transceiver
Stations (210, 220, and 230) is required. This positioning data for
GSM systems can include, for example, a Timing Advance (TA) value,
which corresponds to the amount of time in advance that the MS 200
must send a message in order for the BTS 220 to receive it in the
time slot allocated to that MS 200. When a message is sent from the
MS 200 to the BTS 220, there is a propagation delay, which depends
on the distance between the MS 200 and the BTS 220. TA values are
expressed in bit periods, and can range from 0 to 63, with each bit
period corresponding to approximately 550 meters between the MS 200
and the BTS 220. It should be understood, however, that any
estimate of time, distance, or angle for any cellular system can be
used, instead of the TA value discussed herein.
Once a TA value is determined for one BTS 220, the distance between
the MS 200 and that particular BTS 220 is known, but the actual
location is not. If, for example, the TA value equals one, the MS
200 could be anywhere along a radius of 550 meters. Two TA values
from two BTSs, for example, BTSs 210 and 220, provide two possible
points that the MS 200 could be located (where the two radiuses
intersect). However, with three TA values from three BTSs, e.g.,
BTSs 210, 220, and 230, the location of the MS 200 can be
determined with a certain degree of accuracy. Using a triangulation
algorithm, with knowledge of the three TA values and site location
data associated with each BTS (210, 220, and 230), the position of
the mobile station 200 can be determined (with certain accuracy) by
the Mobile Positioning Center (MPC) 270.
Therefore, Timing Advance (TA) values are obtained from the
original (serving) BTS 220 and two neighboring (target) BTSs (210
and 230). In order for each target BTS (210 and 230) to determine a
TA value, a positioning handover to each of the BTSs (210 and 230)
must occur. A positioning handover is similar to an ordinary
asynchronous handover. The target BTS, e.g., BTS 210, distinguishes
the Positioning Handover from an ordinary handover by a new
ACTIVATION TYPE in the CHANNEL ACTIVATION message. Unlike an
ordinary handover, upon reception of a HANDOVER ACCESS message from
the MS 200, the target BTS 210 only calculates the TA value, and
does not respond to the mobile station 200, that is, no PHYSICAL
INFORMATION is sent to the MS 200. Thus, the MS 200 will then
return to the previous channel allocated by the original BTS 220
after the time period defined by the MS's 200 internal counter
expires, e.g., 320 milliseconds.
Location services have a high potential for invasion of a
subscriber's privacy. This is especially true when commercial
applications are given the ability to access the location services.
Proper authorization and access capabilities must be provided to
prevent misuse and allow the subscriber to have adequate control
over the ability of external parties to determine his or her
location. In addition, these authorization procedures must provide
adequate protection even when the subscriber is roaming.
Currently, authorization procedures exist for only a limited set of
location services. These procedures do not include the ability to
handle roaming subscribers, and can only be applied to services
which have the ability to locate only subscribers within a certain
group (Location of Subscriber within Group (LSG) services). In
addition, the subscriber typically does not have ability to prevent
positioning.
A previously considered solution to the problem of privacy for
positioning includes a subscriber settable option
disabling/enabling all application initiated location capabilities.
However, this option disables all application initiated location
queries, and if the subscriber chooses to enable the application
initiated queries, any agency subscribing to positioning
capabilities, which has the subscriber's number can position the MS
at any time.
Another considered solution would permit positioning by setting an
indicator on the phone. However, enabling positioning is intrusive,
and there is currently no existing mechanism on MSs to enable
positioning. Furthermore, it is difficult for the MS to determine
when the application has finished positioning the MS (multiple
positionings may be required).
Another considered solution would provide a confirmation dialog in
which the subscriber must either permit or disallow the positioning
request. However, this solution is also intrusive. If the user does
not successfully indicate acceptance in the dialog, the positioning
will not occur.
It is therefore an object of the invention to provide authorization
checking of location applications prior to positioning a mobile
terminal within a cellular network.
SUMMARY OF THE INVENTION
The present invention is directed to telecommunications systems and
methods which perform authorization checks prior to allowing a
location service to position a mobile terminal within a cellular
network. The various checks involve ensuring that the requesting
agency has authorization to request positioning of mobile
terminals, determining whether positioning of mobile terminals is
allowed within the cellular network that the mobile terminal is
currently located in, verifying the authenticity of the identity of
the mobile positioning center, ascertaining whether the mobile
subscriber has allowed the requesting agency to position the mobile
terminal, and confirming that all relevant criteria for positioning
have been met by both the mobile subscriber and the requesting
agency. For example, in some circumstances, an agency may only be
permitted to position a mobile terminal while that mobile terminal
has a call established to a specific number (or set of numbers). In
that case, each agency positioning request is screened against a
directory number or set of directory numbers specific to that
agency. The agency requesting the positioning (taxi company,
police, etc.) is interfaced with a location application, which is
interfaced with a local Mobile Positioning Center (MPC). This
location application will request the MPC to position a mobile
terminal with a certain directory number on behalf of a given
agency. The MPC will only permit the positioning to occur if that
mobile terminal currently has a call established to one of the
numbers associated with the given agency. Otherwise, the
positioning request is rejected.
BRIEF DESCRIPTION OF THE DRAWINGS
The disclosed inventions will be described with reference to the
accompanying drawings, which show important sample embodiments of
the invention and which are incorporated in the specification
hereof by reference, wherein:
FIG. 1 is a block diagram of a conventional terrestrially-based
wireless telecommunications system;
FIG. 2 illustrates a sample positioning handover in which
positioning data is acquired by a target base transceiver station
and transmitted to a serving base station controller;
FIG. 3 demonstrates sample steps in an authorization process for
positioning of a specific mobile terminal within a cellular network
in accordance with preferred embodiments of the present
invention;
FIG. 4 describes a sample flow for validating the authority of an
agency to position a mobile terminal based upon criteria to be met
by both the mobile terminal and the requesting agency in accordance
with preferred embodiments of the present invention; and
FIG. 5 depicts steps in a sample positioning process after
authorization for positioning has been obtained in accordance with
preferred embodiments of the present invention.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EXEMPLARY
EMBODIMENTS
The numerous innovative teachings of the present application will
be described with particular reference to the presently preferred
exemplary embodiment. However, it should be understood that this
class of embodiments provides only a few examples of the many
advantageous uses of the innovative teachings herein. In general,
statements made in the specification of the present application do
not necessarily delimit any of the various claimed inventions.
Moreover, some statements may apply to some inventive features but
not to others.
With reference now to FIG. 3 of the drawings, steps in a sample
authorization process for positioning of a specific Mobile Station
(MS) 200 within a cellular network 205 are illustrated. Initially,
when a positioning request is received by a local (serving) or home
Mobile Positioning Center (MPC) 270 (step 300), the local or home
MPC 270 must verify the identity of the requesting agency 280 and
the authority of that agency 280 to request positioning (step 310).
This can be accomplished by the MPC 270 cross-checking the identity
of the requesting agency 280 with a list of agencies (location
nodes) stored within a database 275 the MPC 270 that have the
authority to position mobile stations 200. If the requesting agency
280 is not a valid agency or does not have authority to position
mobile stations 200 (step 310), a message indicating that
positioning is denied is sent to the requesting agency 280 (step
320). The following authorization checks, with the exception of the
verification of the identity of the requesting MPC 270, can be
bypassed if the requesting agency 280 is a law enforcement agency
or an emergency center.
However, if the requesting agency 280 is valid and does have
authority to position mobile stations (step 310), the serving MPC
270 (either home or local depending upon the current location of
the MS 200) can optionally further check the authority of the
requesting agency 280 to position the specific MS 200 requested
(step 330). For example, if the requesting agency 280 is only
permitted to position specific MSs 200 within a group of MSs 200,
e.g., a taxi service connected to the home PLMN 205 can request the
location of taxi mounted MSs, the membership of the specific MS 200
to the group must be confirmed. Typically, the MPC 270 verifies
that the identity of the MS 200 to be positioned, e.g., the
International Mobile Subscriber Identity (IMSI) number, is within a
list of mobile identities allowed to be positioned by the
requesting agency 280. This list could be provided by the
requesting agency 280 when the requesting agency 280 registers with
the home MPC 270, or could be stored in the home MPC 270. If the
specific MS 200 to be positioned has roamed outside of the home
Public Land Mobile Network (PLMN) 205, the serving MPC (not shown)
could then request this list from the home MPC 270. If the identity
of the MS 200 is not within the list of allowable mobile identities
to position, a message indicating that positioning is denied can be
sent to the requesting agency 280 (step 320).
If the subscriber has roamed into a new PLMN (not shown) (step
340), the serving MPC (not shown) must ascertain whether
positioning of MSs 200 is permitted within the serving PLMN (not
shown) (step 350). If positioning of the roaming MS 200 is not
allowed (step 350), a message indicating positioning is denied is
sent to the requesting agency 280 (step 320). Furthermore, the home
MPC 270 may prohibit the serving MPC from positioning the MS 200
when the MS 200 has roamed. The serving MSC/VLR (not shown) must
ascertain whether positioning of the MS 200 is restricted when the
MS 200 is roaming (step 360), e.g., by querying the HLR 265, and if
positioning is restricted (step 360), a denial message must be sent
to the requesting agency 280 (step 320). Alternatively, all
information regarding positioning can be sent to the serving
MSC/VLR when a location update is performed by the MS 200.
If positioning of the MS 200 is allowed in the serving PLMN (step
350 and 360), the serving MSC/VLR must further verify the identity
of the requesting MPC 270 (step 370) by determining the identity of
the home MPC 270, e.g., by querying the Home Location Register
(HLR) 265 or by checking the subscriber record sent by the HLR 265
to the serving MSC/VLR when a location update was performed, and
cross-checking that identity with the identity of the requesting
MPC 270. If the requesting MPC 270 is not the home MPC 270 (step
370), a denial message is sent to the requesting agency 280 (step
320).
Thereafter, the serving or home MSC/VLR 260 checks the subscriber
record obtained from the HLR 265 to ensure that the subscriber
associated with the MS 200 to be positioned has subscribed to the
positioning service offered by the requesting agency 280 (step 380)
and that the subscriber has enabled the positioning by the
requesting agency 280 (step 390). For example, a requesting agency
280 could provide location services for MS-requested positioning.
In that case, the serving or home MSC/VLR 260 must determine
whether the subscriber has subscribed to the location services
provided by the requesting agency 280 (step 380) and whether the
subscriber has enabled the positioning (step 390), e.g., that the
request for positioning came from the MS 200. If the subscriber has
not subscribed to the service or has disabled (or not activated)
the service, a denial message is sent to the requesting agency 280
(step 320)
Finally, the serving or home MPC 270 must validate that all
criteria for positioning has been met (step 395). If so, then the
MS 200 can be positioned (step 398). For example, when an external
agency 280 positions a MS 200 in order to provide a service or
assist the mobile subscriber, the subscriber should be able to
restrict the external agency 280 from positioning the MS 200 if the
mobile subscriber does not need the service. The Location of
Subscriber while Connected (LSC) service provides one way of
accomplishing this. For example, the LSC service can be used by a
taxi service to determine the subscriber's location and then to
dispatch a taxi to that location. In addition, such LSC services
are useful for wrecker company's, and emergency calls.
Such agencies 280 can only position a MS 200 while that MS 200 has
a call established to a specific number (or set of numbers). Thus,
the taxi company could only position mobile stations 200 that
called it's number to order a taxi. Each agency's 280 positioning
requests would be screened by the MPC 270 against a directory
number or set of directory numbers specific to that agency 280.
With reference now to FIG. 4 of the drawings, a sample flow for
validating the authority of an agency 280 to position a mobile
station (MS) 200 based upon criteria to be met by both the MS 200
and the requesting agency 280 is depicted. The agency requesting
the positioning (taxi company, police, etc.) will be interfacing
with a location application 280 (step 400), which is interfaced
with a local Mobile Positioning Center (MPC) 270 (step 410). The
set of directory numbers valid for the agency represented by that
application 280 is communicated to the MPC 270 (step 430) when the
location application 280 registers with the MPC 270 (step 420).
This application 280 will request the MPC 270 to position a MS 200
with a certain directory number on behalf of agency xxx (step 440).
The MPC 270 will only permit the positioning to occur (step 460) if
that MS 200 currently has a call established to one of the numbers
associated with agency xxx (step 450). Otherwise, the positioning
request is rejected (step 470).
With reference now to FIG. 5 of the drawings, after the
authorization of the requesting agency to position the MS has been
confirmed, positioning of the MS 200 continues with the MPC 270
forwarding the positioning request to the serving Mobile Switching
Center/Visitor Location Register 260 (step 500). The MPC 270 can be
located within the MSC/VLR 260, or could be a separate node in
communication with the MSC/VLR 260. The serving MSC/VLR 260 then
forwards the positioning request to the BSC 240 (step 510). If the
MS 200 is in idle mode (not in use), the MSC/VLR 260 must page the
MS 200 and set up a call to the MS 200 prior to forwarding the
positioning request to the BSC 240 (step 510). This call does not
activate the ringing tone on the MS 200, and therefore, is not
noticed by the MS 200.
The originating BSC 240 then determines which Base Transceiver
Station (BTS) 220 is currently serving the MS 200 (step 520), and
obtains a Timing Advance (TA) value (TA1), or other positioning
data, from this serving BTS 220 (step 525), if possible.
Thereafter, TA values are obtained from two target BTSs (210 and
230) (step 560) by performing a positioning handover (step 530). If
the serving BTS 220 does not support positioning, an additional
target BTS (not shown) must be selected. It should be noted that
other positioning methods based on triangulation can be used
instead
of obtaining TA values, as discussed herein. In addition,
positioning of the MS 200 can be performed using more than three
BTSs (210, 220, and 230).
The positioning handover to one of the target BTSs 230 (step 530)
is accomplished by the serving BSC 240 sending a new ACTIVATION
TYPE in a CHANNEL ACTIVATION message to the target BTS 230, which
informs the target BTS 230 that a positioning handover needs to be
performed (step 535). The target BTS 230 then acknowledges the
CHANNEL ACTIVATION message to the serving BSC 250 (step 540).
Thereafter, the BSC 240 sends a command to the MS 200 via the
serving BTS 220 (step 545) to transmit a HANDOVER ACCESS message to
the target BTS 230 (step 550). During the time that the MS 200 is
waiting for a response from the target BTS 230, e.g., around 320
milliseconds, the target BTS 230 measures the Timing Advance value
(access delay) (TA3) (step 555), using access bursts sent by the MS
200, and forwards this positioning data to the serving BSC 240
(step 560). A positioning handover can then be performed to the
other target BTS 210 in the same manner as stated hereinbefore. The
TA value measured by the target BTS 230 (TA3) is then transmitted
by the serving BSC 250 to the MSC 260 (step 565), together with TA
values (TA1 and TA2) obtained from the serving BTS 220 and other
target BTSs 210.
Finally, the TA value acquired from the target BTS 230 (TA3),
together with other TA values (TA1 and TA2) are forwarded to the
Mobile Positioning Center (MPC) 270 from the MSC 260 (step 570),
where the location of the MS 200 is determined using the
triangulation algorithm (step 575). The MPC 270 then presents the
geographical position of the MS 200 to the requesting agency (node)
280 (step 580).
As will be recognized by those skilled in the art, the innovative
concepts described in the present application can be modified and
varied over a tremendous range of applications. Accordingly, the
scope of patented subject matter should not be limited to any of
the specific exemplary teachings discussed.
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